var eles = document.getElementsByTagName('div');
var innerHTML = '<input></input>';
setTimeout(function(){
    eles.innerHTML = '<input>请输入密码</input>';
})
var containerEle = document.getElementsByClassName('container')[0];
containerEle.getElementsByClassName.width = '300px';
containerEle.innerHTML = "<div class=\"text\">" + 
                          "<span>用户名:</span><input/>"+
                          "</div>" +
                          "<div class=\"text\">"+
                          "<span>密码：</span><input class=password>" +
                          "</div>"